The present disclosure relates to establishing Multi-Protocol Label Switching (MPLS) TE Label Switching Paths (LSPs) crossing multiple traffic engineering (TE) information summary areas that hide TE link state information, e.g., topology transparent zones (TTZs). TTZs are generally known in the art, as set forth in U.S. patent application Ser. No. 13/372,592, filed Feb. 14, 2012, by Renwei Li, et al., titled “System and Method for Topology Transparent Zoning in Network Communications” (herein, “the '592 application”) and Ser. No. 13/646,481, filed Oct. 5, 2012, by Renwei Li, et al., titled “Simple Topology Transparent Zoning in Network Communications” (herein, “the '481 application”), both incorporated herein by reference.
The number of routers in an Autonomous System (AS) grows with Internet traffic. As a result, the sizes of Open Shortest Path First (OSPF) Link State Databases (LSDBs), TE Databases (TEDs), and OSPF routing tables may increase. Any link state change including TE link state change in an AS may lead to a number of link state distributions to every router in the AS.
Internet Engineering Task Force (IETF) Request for Comments (RFC) 2328, entitled “OSPF Version 2,” describes OSPF areas in an AS. Each area may have a number of area border routers connected to the backbone area. A big AS may be divided into a number of OSPF areas. The TE link state in one area may not be distributed to other areas. Thus, there may be a number of issues when an AS or an area is split further into multiple areas.
Under current practice, it may be difficult to establish an MPLS TE LSP crossing multiple areas. In general, a TE path crossing multiple areas may be computed by using collaborating path computation elements (PCEs) through the PCE communication protocol (PCEP), which may not be easy for operators to configure since manual configuration of the sequence of domains is required. Further, the current PCE method may not guarantee that the path found would be optimal. Further, under current practice, TE information about one or more links inside the zone may require distribution and storage in a router. This may lead to large TE link state databases in routers, which may not be ideally scalable.